Yumi Fukuzawa is the central character. She begins as a shy and insecure freshman at Lillian Girls' Academy, her timidity often making her emotions visibly apparent on her face. An early encounter where Sachiko Ogasawara fixes Yumi's tie leaves her mortified, establishing initial self-doubt. Sachiko unexpectedly offers Yumi her rosary to become her *petite sœur* within the Yamayurikai, primarily to avoid playing Cinderella alongside her male cousin and fiancé, Suguru Kashiwagi. Feeling hurt at being chosen for convenience, Yumi initially refuses. However, after witnessing Sachiko's emotional turmoil regarding her arranged marriage and seeing her cry, Yumi later accepts the rosary during a bonfire following the school festival, formally entering their sisterly bond. Her relationship with Sachiko forms a core aspect of her development. Yumi demonstrates deep loyalty and a desire to support Sachiko, learning to navigate Sachiko's complexities, including her aversion to men stemming from family dynamics where male relatives openly kept mistresses. This loyalty is tested when Sachiko's cousin, Touko Matsudaira, arrives, sparking jealousy in Yumi due to Touko's closeness with Sachiko. Despite this, Yumi remains supportive, especially during Sachiko's grief over her grandmother's death. Yumi also maintains significant relationships with others, notably Sei Satou. Sei frequently teases and hugs Yumi, considering her cute, which occasionally triggers Sachiko's jealousy. Sei credits Yumi with giving her a reason to live during exam periods. Yumi's character evolution becomes increasingly evident. She gradually matures from her initial shyness, developing greater independence, calmness, and collectedness. This growth accelerates after Touko enters her life and as she takes on more responsibilities within the Yamayurikai. By the time of the third season OVAs, this development manifests in proactive decisions. For instance, during a summer retreat at the Ogasawara home, Sachiko's acquaintances attempt to humiliate Yumi due to jealousy of her relationship with Sachiko. Pressured to perform musically at a party, Yumi chooses to sing "Maria-sama no Kokoro," with Sachiko accompanying her on piano. The heartfelt performance impresses the elderly great-grandmother guest, defusing the situation and earning Yumi an invitation to return the following year. Furthermore, Yumi demonstrates newfound confidence and ethical consideration in her leadership role. She organizes a meeting between the Yamayurikai and the all-boys Hanadera student council but initially plans to trick Sachiko into attending due to Sachiko's dislike of men. Feeling this approach betrays trust, Yumi confesses her intentions. She argues Sachiko should attend voluntarily to prepare for future similar situations. Sachiko acknowledges Yumi's improved ability to handle her and agrees to attend willingly. As she advances to her second year, Yumi is tasked by Sachiko to find her own *petite sœur*, signifying her rising status and responsibilities within the council. She eventually takes Touko as her *petite sœur* after persistent efforts. Touko, initially rejecting Yumi due to her own insecurities stemming from being an orphan adopted after her biological parents died in an accident, eventually accepts the rosary after Yumi helps her confront her past and feelings of unworthiness. Her name, meaning "help, assist" (佑) and "snake, serpent" (巳), reflects her supportive nature.